It appears there may be a bit of a mix-up here. CNN does not finalize rules for presidential debates; this is typically the job of the Commission on Presidential Debates, a non-profit, non-partisan organization that has organized general election presidential debates in the United States since its establishment in 1987.
Additionally, RFK Jr. refers to Robert F. Kennedy Jr, who is an environmental lawyer and activist. He is not currently a presidential candidate in any mainstream political party, so it would be unlikely for him to participate in a debate with current President Biden and former President Trump. If there has been a recent change in this situation, additional information would be needed to provide accurate assistance.
